blazes and wither skeletons are spawning nearly 50 at a time (not an expression their was around about 50 of them) in easy mode

What I expected to happen was...:
the amount of mobs should of been a lot smaller

What actually happened was...:
well to put it simple blazes were spawing 5 at a time and the same was with wither skeletons

Steps to Reproduce:
1. go to a nether fortress
2. turn on a dificulity
3. and you will die if you have no armour